Air is supplied to an internal combustion engine of a vehicle from outside so as to combust fuel during an operation of the engine. When the air inflowing from the outside includes dusts, friction between an inner wall of a cylinder and an outer surface of a piston is increased, thus reducing the lifespan of the engine. A conventional engine has an inlet of an intake manifold forming a distribution passage of air and coupled with an air cleaner. The air cleaner filters debris in the atmosphere to supply purified air to the engine. Therefore, the air cleaner reduces abrasion of an engine piston ring to maintain engine performance.
However, when the inflow of debris is excessive, ventilating resistance is increased, which affects an engine output. Therefore, after the air cleaner is used for a predefined period of time, a filter of the air cleaner needs to be replaced. FIGS. 1A and 1B are diagrams illustrating an air cleaner structure in accordance with the related art. Debris may flow into an engine through an engine intake passage at the time of replacing or cleaning a filter of an air cleaner in accordance with the related art, thus deteriorating the engine piston ring.
To solve the above problem, a structure in which two filters are mounted as a main element with a safety element (see FIG. 1B). Therefore, even though the main element is cleaned or replaced, it is possible to block the debris from inflowing into the engine due to the safety element. However, the safety element is additionally required, which needs to be replaced after using for a predetermined period of time, thereby increase cost.